So You Want to Do a Project about Lung Capacity!
To measure the lungs' air capacity.
- masking tape
- I-gallon (4-L) hard plastic or glass jug with lid
- I-cup (250-mL) measuring cup
- marking pen
- blue food coloring
- large plastic dishpan
- 2-foot (60-cm) piece of aquarium tubing
- drinking straw
- Place a strip of masking tape down the side of the jug.
- Use the measuring cup to add 16 cups (4 L) of water to the jug, 1 cup (250 mL) at a time. Use the marking pen to mark a line on the tape to indicate the level after each cup of water.
- Add 20 or more drops of food coloring to the water. Secure the lid on the jug, then shake the jug to mix the water and food coloring.
- Fill the dishpan about half full with water.
- Place the jug upside down in the dishpan and remove the lid.
- Ask your helper to hold the jug. Do not allow air bubbles to enter the jug.
- Place about 4 inches (10 em) of one end of the tubing into the mouth of the jug.
- Insert the drinking straw into the free end of the tubing to make a sanitary mouthpiece.
- Take a normal breath and exhale (breathe out) through the straw into the tubing.
- Use the scale on the jug to determine the volume (amount of occupied space) of your exhaled breath in cups. Estimate the volume between marks to the nearest one-fourth cup (0.63 mL). Record this measurement as tidal air in a Lung Capacity Data table like the one shown.
- Empty the jug and pan and repeat steps 3to 8.
- Inhale normally and exhale through the straw into the tubing, making an effort to force all the air from your lungs. Record this measurement as tidal air plus reserve air. Subtract the tidal air volume and record the results as reserve air.
- Repeat step 11, then inhale deeply and force all the air you can from your lungs. Record this measurement as vital capacity (maximum volume of air that can be inhaled or exhaled during forced breathing). Vital capacity is the tidal air plus reserve air plus complemental air (the volume of air that can be inhaled with force).
- Subtract the reserve air from the vital capacity to calculate complemental air, then enter your results in the data table.
When the lungs are filled, they hold varying volumes of air depending on the size of the person. The author's lungs hold about 14 cups (3,687 mL). About 5 cups (1,438 mL) of this amount is tidal air. Tidal air is the volume of air involved during normal, relaxed inspiration (breathing in) and expiration (breathing out). The volume of air that can be forced out after normal expiration is called reserve air, and the volume of air that can be inhaled with force is called complemental air. With vigorous inspiration and expiration, the tidal air plus reserve air plus complemental air (or total vital capacity) can be expelled. Even with maximum expiration, the lungs are not empty. For adults, depending on size, there is always about 4 cups (1 L) of air that remains in the lungs, and this volume is referred to as residual air.